Op Tech Flashcards
Cavo-surface margin angle
- the angle at the junction between the prepared and unprepared surfaces
- should be between 60-120 degrees, 90 ideally
cavity margins
the junction between the walls of the cavity and the unprepared tooth surface
line angles
the line formed at the junction between two surfaces within the cavity
point angles
the angle formed between three prepared surfaces in the cavity
occlusal floor
the surface at the bottom of the cavity, parallel to the occlusal plane, that lies over the pulp
gingival floor
the surface at the bottom of the cavity, parallel to the occlusal plane, bound by the gingival margin
axial wall
a vertical wall within the cavity that is parallel to the long axis of the tooth
pulpal axial wall
axial wall that surrounds the pulpal tissue
buccal / lingual axial wall
axial wall that forms the border of the cavity, bounded by the Cavo-surface margin
flat plastic
manipulation of shapeable materials ie composite or glass ionomer
matrix band
used to rebuild margin walls
excavator
removal of caries or thinned enamel, removal of materials
tweezers
handling small objects ie wedges
mirror
viewing intraorally, tissue retraction
Describe the dentine bonding process.
- acid etch applied (35% phosphoric acid), opens tubules by removing smear layer, leaving collagen network, increased wettability
- prime and bond applied, primers hydrophilic end binds to the hydrophilic dentine tubules, the hydrophobic methacrylate binds to the hydrophobic adhesive
What is in prime and bond?
HEMA
resin bis-GMA
camphorquinone
acetone
What are the principles of caries removal?
- Identify and removal carious enamel.
- Remove enamel to identify the extent of caries and the ADJ.
- Progressively remove caries in dentine, from ADJ and circumferentially deeper.
- Remove deep caries over the pulp.
- Modify cavity design, smooth edges, prepare for chosen filling material (ie retentive form = amalgam).
- Smoothing of internal line and point angles.
- Smoothing of the Cavo-surafce margins.
What are the components of a dental handpiece?
- head (bearings, rotor, chuck, bur, backcap)
- neck
- body
- coupler
What are the safe for use checks?
- check the backcap doesn’t rotate anticlockwise
- apply tension to bur to ensure it doesn’t come loose
- apply tension to the coupling to ensure it doesn’t come loose
What are the fit for use checks?
- bur rotates freely
- apply lateral tension to the bur
- run device for >5s to ensure regular high pitch noise and bur rotates on its own axis
What are the components of composite resin?
- filler particles
- resin
- camphorquinone (photointiator)
- low weight dimethacrylates
- silane coupling agents
What is an example of a filler particle in composite resin?
- microfine silica
- quartz
What is an example of a resin in composite resin?
bisGMA
What is an example of a low weight dimethacrylate in composite resin?
- Triethylene glycol dimethacrylate (TEGDMA)
- adjusts viscosity and reactivity
What is silane coupling agent in composite resin?
- allows for an intimate bond between the filler particles and the resin
What is DOC?
- depth of cure
- typically 2mm
- the depth at which the material is at 80% of the hardness of the surface
How is polymerisation contraction shrinkage avoided in cavities?
- two opposing surfaces should not be connected by a layer of composite
- build in triangular increments
What is in the powder component of RMGIC?
- fluoro-alumino-silicate glass
- barium glass (radiopacity)
- vacuum dried polyacrylic acid
- potassium persulphate
- ascorbic acid
What is in the liquid component of RMGIC?
- HEMA
- polyacrylic acid with methacrylate groups
- tartaric acid
- water
- camphorquinone
Describe the technique used for taking an impression.
- size check the tray
- retract cheek
- rotate tray from 90 degrees into the mouth
- retract lip and line up the midline with the handle
- seat the tray at the posterior and then the anterior
- arrange the buccal and labial tissues to ensure proper impression of sulcus
Maxillary stand behind
Mandibular stand in-front
How does temperature affect alginate setting times?
Hot = faster set
What makes up the liquid component of GIC?
- polyacrylic acid
- tartaric acid
- itaconic aci d
What makes up the powder component of GIC?
- silica
- alumina
- various salts (including calcium fluoride, sodium fluoride, aluminium fluoride, and aluminium phosphate)
What are the 3 phases of GIC setting reaction?
- dissolution
- gelation
- hardening
Describe the setting reaction of RMGIC.
Dual cure reaction
- polymerisation reaction initiated by camphorquinone and light blue cure (initial set)
- acid-base reaction as in GIC (over 24 hours)
Tri cure reaction
- polymerisation reaction initiated by camphorquinone and light blue cure (initial set)
- REDOX reaction “dark cure” (5 minutes)
- acid-base reaction as in GIC (over 24 hours)
What problems does light curing pose?
Safety risk
- exothermic reaction (could be damaging to the pulp)
- thermal trauma to patient soft tissues if optic rod not placed correctly
- ocular damage to operator (omitted by use of safety shields or glasses)
Setting
- larger increments placed than the DOC
- polymerisation contraction shrinkage
How do you mix GIC?
- 2 scoops of powder to 2 drops of water
- 1 dry side and 1 wet side of spatula
- mix one scoop of powder at a time
- wipe spatula immediately after mixing
How is RMGIC dispensed?
- capsule “popped”
- mixed for 8 seconds
- silver gun dispenses (fugi)
OR - as two pastes, clicked out together and mixed (vitrebond)
What are the components of calcium hydroxide cement?
Paste 1
- calcium hydroxide
- zinc oxide
- zinc stearate
- ethyl toluene sulphonamide
Paste 2
- glycol salicylate
- titanium dioxide
- calcium sulphate
- calcium tungstate
What can calcium hydroxide be used as?
- cavity liner
- pulp cap
What is ZOE?
- zinc oxide eugenol cement
What is ZOE used for?
- cavity liner / base
- temporary restorations
- root canal sealer
- periodontal dressings
How do you mix calcium hydroxide?
- a pea sized amount of base paste is dispensed
- a pea sized amount of catalyst is added and the two mixed together until a uniform colour is reached
- wipe the spatula clean
What is the setting reaction of calcium hydroxide cement?
acid-base reaction
What is the setting reaction of ZOE cement?
acid-base reaction, chelation
What is the purpose of using dental dam?
- airway protection (!)
- field isolation
- improved vision
What material is used for dental dam?
nitrile
What is the purpose of floss ligatures?
- invert the dam into the gingival margin
- creates a good seal
